1. Field of the Invention
The present invention relates to a lubricant supplying device, an image forming apparatus, and a process cartridge.
2. Description of the Related Art
In image forming apparatuses such as printers, facsimiles, and copying machines, the image forming apparatuses have been known that include lubricant supplying devices supplying lubricant to surfaces of image carriers for protection or reducing friction of photosensitive elements serving as lubricant supply targets and intermediate transfer belts serving as image carriers (e.g., Japanese Patent Application Laid-open No. 2007-293240).
FIG. 20 is a schematic structural view of a lubricant supplying device described in Japanese Patent Application Laid-open No. 2007-293240. FIG. 20(a) illustrates a state at the beginning of use. FIG. 20(b) illustrates a state at which solid lubricant 162 is exhausted. FIG. 20 illustrates a structure on one end side in a longitudinal direction of the solid lubricant 162. The other end side also has the same structure. As illustrated in FIG. 20(a), the lubricant supplying device described in Japanese Patent Application Laid-open No. 2007-293240 includes a supplying member 161 that abuts the solid lubricant 162 having a bar shape, scrapes the solid lubricant 162 by making a sliding contact with and rubbing the solid lubricant 162, and supplies the powdered lubricant after the scraping to an image carrier. In addition, the lubricant supplying device includes a pushing mechanism 163 that pushes the solid lubricant 162 and a lubricant holding member 164 toward the supplying member 161. The lubricant holding member 164 holds a side of the solid lubricant 162 opposite the side with which the solid lubricant 162 abuts the supplying member 161 and is provided in a case 165 of the lubricant supplying device such that the lubricant holding member 164 can approach to and leave from the supplying member 161.
The pushing mechanism 163 has a pair of swing members 163A, one end side of each of which is supported by the lubricant holding member 164 in a rotatable manner, disposed symmetrically about the center in the longitudinal direction of the solid lubricant 162 (the swing member 163A disposed on the other end side in the longitudinal direction of the lubricant holding member 164 is not illustrated). Respective both ends of a spring 163C serving as a biasing unit are attached to the swing members 163A. Each swing member 163A receives from the spring 163C a biasing force acting toward the center in the longitudinal direction of the lubricant holding member 164 as illustrated with arrow D in FIG. 20(a). The biasing force urges the other end side (hereinafter referred to as a swing end) of each swing member 163A to leave from the lubricant holding member 164 as illustrated in FIG. 20(a), resulting in the swing end abutting a surface 165A facing the lubricant holding member 164 of the case 165. The lubricant holding member 164 abuts the supplying member 161 with a certain abutting force by being pushed toward the supplying member 161 by a reaction force of a pushing force of the swing members 163A (force acting downward in FIG. 20(a)) applied to the surface 165A of the case 165.
With the rotation of the supplying member 161, the supplying member 161 makes a sliding contact and rubs the solid lubricant 162, which abuts the supplying member 161. Lubricant scraped from the solid lubricant 162 by the sliding contact and rubbing and stuck to the supplying member 161 is applied to a surface of the image carrier. As the solid lubricant 162 is gradually scraped by the sliding contact and rubbing of the supplying member 161, the swing members 163A swing, resulting in the lubricant holding member 162 moving toward the supplying member 161 as illustrated in FIG. 20(b). The solid lubricant 162 continues to abut the supplying member 161 from the beginning to an end stage of use, thereby enabling the supplying member 161 to scrape the solid lubricant 162 well.
When image forming operation is performed without supply of lubricant, the image carrier is damaged by being worn because no protective action of the lubricant is provided. Japanese Patent Application Laid-open No. H8-314346 describes a lubricant supplying device that detects a near-end of lubricant. FIG. 21 is a schematic perspective view illustrating a lubricant near-end detecting unit of the lubricant supplying device described in Japanese Patent Application Laid-open No. H8-314346. As illustrated in FIG. 21, the lubricant near-end detecting unit includes a lubricant holding member 173 that holds solid lubricant 170 and has electrical conductivity, and a first electrode member 181 that abuts one end of the lubricant holding member 153 and a second electrode member 182 that abuts the other end of the lubricant holding member 173 at time when an amount of the remaining lubricant is small. The first electrode member 181 and the second electrode member 182 connect to a detecting circuit 183, which is connected to a display circuit 184 and applies a voltage between the electrode members 181 and 182 and detects whether a current flows. The lubricant holding member 173 is urged by springs 172 to abut a supplying member (not illustrated).
At the beginning of use, the lubricant holding member 173 and the electrode members 181 and 182 have a distance therebetween and thus no current flows between the electrode members. As the solid lubricant 170 is gradually scraped by the supplying member (not illustrated) making a sliding contact with and rubbing the solid lubricant 170, the lubricant holding member 173 moves toward the supplying member by a biasing force of the springs 172. At the near-end of the solid lubricant 170, the conductive lubricant holding member 173 abuts the first electrode member 181 and the second electrode member 182. As a result, a current flows between the electrode members 181 and 182, and the detecting circuit 183 detects the near-end of the solid lubricant 170.
In the lubricant near-end detecting unit of the lubricant supplying device described in Japanese Patent Application Laid-open No. H8-314346, the lubricant holding member just abuts the electrode members and establishes conduction therebetween at time when an amount of the remaining lubricant is small. The lubricant holding member and the electrode members have a distance therebetween during a period until an amount of the remaining lubricant becomes small from the beginning of use. Accordingly, during the period of time until an amount of the remaining lubricant becomes small, the lubricant may stick to areas of the electrode members where the electrode members abut the lubricant holding member and areas of the lubricant holding member where the lubricant holding member abuts the electrode members. The lubricant stuck to the abutting areas hinders conduction from being established in the abutting areas though the lubricant holding member and the electrode members are abutted. As a result, the near-end of the lubricant may not be detected.
Particularly, the lubricant holding member, which holds the solid lubricant, is disposed under an environment in which the lubricant readily sticks to the lubricant holding member. Accordingly, an amount of lubricant stuck to the areas of the lubricant holding member where the lubricant holding member abuts the electrode members becomes large, thereby readily causing misdetection to occur due to the sticking of lubricant.
In view of the above, there is a need to provide a lubricant supplying device that can reliably detect that an amount of the remaining solid lubricant is equal to or smaller than a certain amount, and an image forming apparatus and a process cartridge using the lubricant supplying device.